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Mendelian Genetics. Extending Mendelian Genetics. C W C W. C R C R. C R C W. Incomplete Dominance. Heterozygous phenotype is intermediate. C W C W. C R C R. C R C W. C R C W. C R C W. Incomplete Dominance. 1 : 2 : 1. Codominance.
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Mendelian Genetics Extending Mendelian Genetics
CWCW CRCR CRCW Incomplete Dominance • Heterozygous phenotype is intermediate
CWCW CRCR CRCW CRCW CRCW Incomplete Dominance 1 : 2 : 1
Codominance • The heterozygous phenotype represents both alleles • Cattle coat color Alleles C = Red coat C’ = White coat Genotype C’C’ CC CC’
Codominance • Tay-Sachs Disease Alleles T = functional lipase T’ = dysfunctional lipase GenotypesmPhenotypeMPhenotype T’T’ TT TT’ lipid buildup in brain (fatal) catabolism of lipids (normal) catabolism of lipids (normal)
Multiple Alleles • More than two alleles exist for a gene • Human blood type
Multiple Alleles Genotype Antibodies Blood Type
Polygenic Traits • Human Skin Color • Controlled by at least 3 genes (A, B, and C) • AABBCC = Darkest • 6 copies of melanin-producing alleles • aabbcc = Lightest • 0 copies of melanin-producing alleles • Like other traits, environment is a significant factor in expression